Trichocerca cavia (Gosse, 1886)

Trichocerca cavia (Gosse, 1886) View in CoL ( Figs. 6A View Fig , 7A View Fig )

ỄǕflḆệ ( ljạ)

Coelopus cavia Hudson & Gosse, 1886: p. 69 , pl. XX, fig. 22.

Material examined. Female , glycerol permanent slide ( NIBRIV0000919540 , NIBRIV0000919546 , NIBRIV 0000919547 ). Pond in Seogwipo-si ( 33°25 ʹ 13.1 ʺ N, 126° 50 ʹ 42.1 ʺ E), 09 Jan. 2022. Collected by Su-Jung Ji GoogleMaps .

Diagnosis. Body short and stubby, 115 μm in length. Head part divided from body by transverse folds. Two broad and equal length of spines present on head. Foot located ventrally, and clearly distinguished from body. Two toes equal in length, 30 - 35 μm, and curved ventrally. One large cerebral eyespot located near the posterior brain. Trophi large and asymmetrical, 43μm in length. Left manubrium larger and thicker than right manubrium, with crutched expansion distally. Left manubrium 28 μm in length, and right manubrium 23 μm. Fulcrum straight in dorsal view, with small expansion distally, 32 μm in length. Rami asymmetrical, left alulae directed laterally and right alulae directed posteriorly. Left uncus with large blunt teeth, and right uncus with several small teeth.

Distribution. Cosmopolitan ( Segers, 2007).

Remarks. Trichocerca cavia is most similar to T. bidens (Lucks, 1912) in its stubby body, ventrally positioned foot, and two toes of equal length. However, these two species can be distinguished by the shape of the left manubrium of the trophi. The left manubrium of T. cavia has

A B

a crutch-like distal end, whereas that of T. bidens is simply curved inward. Additionally, these two species differ in both body and trophi size, with T. cavia generally being smaller than T. bidens in all respects. According to the classifications of Koste (1978) and Shiel and Koste (1992), these species can also be differentiated by the presence of anterior spines: T. cavia lacks spines on the anterior margin of the head, whereas T. bidens possesses two broad spines of equal length. However, previous studies have indicated that the presence of anterior spines may not serve as a reliable distinguishing characteristic, as T. cavia has also been reported to possess anterior spines ( Carlin, 1939; Donner, 1950; Pejler, 1962; Chengalath and Mulamoottil, 1975; De Smet, 1993). The Korean specimens examined exhibit two anterior spines, but the trophi characteristics and body size align with those of T. cavia .

Molecular analysis. Genomic DNA was extracted from each of the three specimens, and partial COI sequences were obtained (759 bp, PQ594392-PQ594394). No intraspecific variation was found. Interspecific variation was calculated using 10 Trichocerca COI sequences (582 bp), with variation ranging from 16.5 to 31.1% (Table 3).